jones



July 24, 1956 w. JONES CORRCSION INHIBITING Filed May 19, 1952 FIG. 2

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LQYD W. JONES -6685 A T TORNE Y 2,756,211 CORROSION INHIBITING Loyd W.Jones, Tulsa, Okla, assignor to Stanolind Oil and Gas fiompany, Tulsa,Okla., a corporation of Delaware Application May 19, 1952, Serial No.288,705 12 Claims. (Cl. 252-855) This invention relates to inhibitingcorrosion caused by hydrogen sulfide, carbon dioxide,low-molecularweight organic acids, combinations of these materials, orcombinations of each with oxygen or with each other and oxygen. Moreparticularly, it relates to treating wells to mitigate metal corrosionand associated difiiculties.

Several inhibitors for hydrogen sulfide corrosion have been developed inrecent years. For example, formaldehyde is such an inhibitor which maybe employed in the absence of oxygen. In the presence of both oxygen andhydrogen sulfide, however, formaldehyde is no longer an effectivecorrosion inhibitor. The same is true for the imidazoline derivativeswhich have enjoyed considerable commercial success as hydrogen sulfidecorrosion inhibitors.

When inhibitors for oxygen corrosion are investigated, it is found thatin the presence of a combination of oxygen and hydrogen sulfide even thefatty acids and amines, which form protective films on the metalsurfaces to be protected, are ineffective due to pitting. That is,although most of the surface is protected and weight measurements afterexposure to the corrosive conditions indicate only moderate loss ofweight, a very rapid and severe corrosion takes place in small areas toform deep pits which quickly penetrate the entire metal thickness. Eventhe cyclohexylamine salts of acids from hydrocarbon oxidation, assuggested in U. S. Patent 2,330,524 to Shields has been found to beineffective to prevent combined oxygen and hydrogen sulfide corrosion,although the combined inhibiting abilities of an amine and a fatty acidare available.

The effects of the combined corrosive action of oxygen and hydrogensulfide are particularly noticeable in wells producing sour crude oilaccompanied by brine. In some wells of this type, it is possible toexclude air from the well and thus avoid the effects of oxygen. In manyapplications, however, air has access to the well. For example, the wellmay be pumped with open casing, permitting air to enter the annularspace between the tubing and casing. In gas drive operations, in whichair is employed as the driving gas, a large amount of oxygen may enter aproducing well from the formation, resulting in a very aggravated typeof corrosive condition. Even if natural gas were employed as the drivinggas, leakages in the system usually result in a small percentage of airbeing present in the gas. In wells being produced byhydraulically-actuated bottom-hole pumps, the power oil carries oxygento the bottom of the well where it may enter crude oil containinghydrogen sulfide. The problem becomes particularly serious in air-liftoperation of wells producing sour crude and brine.

Many wells suffer corrosion due to low-molecularweight organic acids,especially those acids containing 2 to 4 carbon atoms per molecule.Inhibitors are known for such a type of corrosion, but many of them suchas ammonia and sodium chromate are ineffective in the presence of eitherhydrogen sulfide or oxygen or both of these gases. On the other hand,inhibitors such as formaldehyde, efiective for hydrogen sulfide alone,are ineffective in the presence of low-molecular-Weight organic acids.

A particularly severe problem exists when all three corrosive agents,that is, hydrogen sulfide, oxygen and lowmolecular-weight organic acids,are present simultanited States Patent neously with water, as, forexample, in tertiary recovery by underground combustion.

In many cases, the effects of corrosion and wear enhance each other. Forexample, in a pumping well, the rubbing of the rods on the tubing tendsto wear through the tubing. This effect is greatly accelerated if acorrosive liquid is present. Some inhibitors, such as the higher fattyacids, form a type of film which prevents both wear and certain types ofcorrosion. But the higher fatty acids are ineffective in the presence ofhydrogen sulfide and, accordingly, wear and corrosion proceed in a mostaggravated form in the presence of this corrosive material even in areasin which corrosion in the absence of wear is only a minor problem.

There is considerable evidence that the same local electrolytic cellswhich are responsible for much of the corrosion of metals, are alsoresponsible for other effects such as the deposition of paraifin in welltubing. An effective neutralization of such cells would be desirable asa means for mitigating not only corrosion, but other effects such asparafiin deposition.

Although the problems are particularly serious in oil wells, the sametroubles are also present in other systems such as in surface injectionequipment for water-flooding operations in which the injected watercontains hydrogen sulfide, carbon dioxide, low-molecular-weight acids,or combinations of each with oxygen or with each other and oxygen. Itwill be apparent, also, that corrosion due to these materials or variouscombinations thereof often occurs outside the petroleum industry andrequires a solution there.

Accordingly, it is aprincipal object of this invention to provide aninhibitor for the corrosive action in the presence of water, of hydrogensulfide, carbon dioxide, low-molecular-weight organic acids,combinations of these materials, or combinations of each with oxygen orwith each other and oxygen.

A more particular object of my invention is to provide a method ofinhibiting the corrosion of ferrous metal parts in wells by thecorrosive action of the above-mentioned materials or combinationsthereof.

An additional object of the invention is to provide a well-treatingmethod to mitigate the effects, such as paraffin deposition, oftenassociated, like corrosion, with localized electrolytic cells in metalsurfaces in wells.

Another object is to provide a remedy to the combined action of wear andcorrosion which often occurs even in areas which corrosion alone is onlya minor problem.

In general, I accomplish these objects by use of a combination of anamine and an organic acid falling within certain molecular weightranges. For example, the octadecyl amine salts of acids produced by theliquid phase partial oxidation of kerosene in a process such as theBurwell process (as described in U. S. Patent 1,690,769) have been foundto be satisfactory for my purposes. Test panels exposed to brinescontaining hydrogen sulfide and air, where an amine-acid complex ofthese materials was employed as an inhibitor, remained substantiallyfree from corrosion both of the general and pitting type. This was trueeven when the ratio of air to hydrogen sulfide was in thehighly-corrosive range of about to l to be expected in air-liftoperations.

Representative test panels are illustrated in the accompanyingphotographs. All figures show test panels subjected to the conditionsoutlined in Example I below employing various inhibitors. I

Figure 1 illustrates the effectiveness of the octadecyl amine salts ofAlox 425 acids produced by the liquid phase oxidation of petroleumhydrocarbons.

Figure 2 shows the effects of using the octadecyl amine alone.

Figure 3 exhibits the efifects of employing the Alox 425 acids alone.

Figure 4 demonstrates the corrosion-inhibiting ability of an acid-aminecomplex in which Alox 425 acids were employed, but the amine was decylamine.

Figure shows the results of substituting octyl amine for the decyl amineemployed in obtaining the panel shown in Figure 4.

Figure 6 illustrates a panel obtained by substituting acetic acid forAlex 425 acids, octadecyl amine being employed as the amine portion ofthe inhibitor.

Comparison of Figures 1, 2 and 3 shows clearly that the inhibitingability of the amine-acid complex is a combination effect not obtainedwith either the acid or amine alone. Both Figures 2 and 3 show the goodprotection of a part of the metal surface, while other parts are badlycorroded.

The panel shown in Figure 4 demonstrates the ability of the decyl aminecomplex to give uniform protection of the entire surface so that anycorrosion which does occur is spread out over the entire area and doesnot quickly penetrate at any one point. A comparison of Figures 4 and 5shows the rather surprisingly sharp division between operable andinoperable amines at about carbon atoms per molecule.

In Figure 6 can be observed the scattered pitting type corrosion whichoccurs when the amine salts of watersoluble organic acids are employedas inhibitors. The pits will of course, quickly penentrate the metalthickness, so the very eflective protection of most of the surface is oflittle value.

The amine-acid complexes are efiective not only in the mitigation ofcorrosion due to hydrogen sulfide, oxygen, or combinations of thesematerials, but also are effective in inhibiting corrosion due tolow-molecular-weight organic acids such as those found in high-pressurecondensate wells. Thus, the materials are applicable not only tosecondary recovery projects in which air is in jected intohydrogen-sulfide-containing formation intentionally or inadvertently,but are particularly applicable to underground combustion projects inwhich low-molecular-weight acids are produced in the combustion zone andlater appear at the output wells together with oxygen and hydrogensulfide.

I believe the theory of my invention to be as follows, although it willbe understood that my invention is not limited thereto. The theory isbased on the well-known occurrence of localized electrolytic cells onsurfaces of metals. Either the amines or the acids appear to becomerather strongly adsorbed on the entire surface of the metals, and thisadsorbed film is suificiently tight over both positive and negativeareas of localized electrolytic cells to inhibit a high percentage ofthe corrosion in the presence of oxygen and water alone. Dr. Zismanswork at the Naval Research Laboratory fully supports this observation.(NRL Report 3680, obtainable as PB 101874 from U. S. Department ofCommerce.) In the presence of a combination of oxygen, water, andhydrogen sulfide, however, neither the acids nor the amines are heldwith sufficient force over the entire metal surface to preventcorrosion. It is believed probable that the acids are not only adsorbed,but may be chemisorbed on positive areas of localized electrolyticcells. That is, they may be bound by forces approaching those involvedin chemical reactions. On negative areas of the cells, however, simpleadsorption forces are probably involved between the surface and theacids. It is believed to be probable that the amines are chemisorbed onnegative areas and simply adsorbed on positive areas.

.If the above theory is correct, a simple adsorbed layer is apparentlysuflicient to protect a surface from oxygen corrosion, but isinsufiicient to prevent penetration by a combination of hydrogen sulfideand oxygen. Thus, an acid layer may fail to prevent corrosion ofnegative areas, while an amine layer may fail to protect the positiveareas when both hydrogen sulfide and oxygen are present. By the use ofboth an amine and an acid, a chemisorbed layer is perhaps formed overall areas, the electrolytic cells being effectively neutralized, thuspreventing substantially all corrosion whether by the independentcorrosive actions of hydrogen sulfide, low-molecular-weight acids, orcarbon dioxide alone, or by combinations of these corrosive agents witheach other or with oxygen. A much longer film life would be expected ifthis theory is correct.

Since the negative and positive areas of the electrolytic cells would besubstantially neutralized, according to this theory, prevention ofparaflin deposition due to the effects of these areas would also beexplained.

In the above discussion, rather general reference has been made toamines and acids. As earlier pointed out, however, some of theamine-acid salts or complexes are inoperable as corrosion inhibitors inthe presence of a combination of hydrogen sulfide and oxygen. Both theamine and the acid must be carefully selected. For example, testsindicate clearly that an amine must be selected which contains at least10 carbon atoms per molecule. The exact reason for this limitation isnot well understood. It is perhaps due to the higher solubility of thelower-molecular-weight amines in both water and oil. It might also bedue to the inability of a short hydrocarbon portion of the amine to forma film of sufiicient thickness to prevent penetration by corrosivematerials. Reduced lateral cohesive forces between the shorter moleculesmight also be responsible. Probably all the factors contribute to thefailure of inhibitors prepared from amines having less than 10 carbonatoms per molecule. Although the IO-carbon amines have proved effective,the higher solubility usually results in a film lost relatively quicklyto the oil and water. For this reason, an amine having at least 12 or 14carbon atoms is generally preferred.

An upper limit of about 20 carbon atoms should also be observed in thecase of amines simply because of the difliculty of dissolving theamines, or even amine-acid complexes in an oil to permit application tothe surfaces to be protected. By use of special solvents such asbenzene, carbon tetrachloride, ethanol, or the like,highermolecular-weight amines and their complexes with organic acids canbe employed. Increased solubility of high-molecular-weight amines canalso be achieved by use of lower-molecular-weight acids or mixtures ofacids.

I have found that many types of amines can be employed within thelimitations set forth above. Thus, the amines may be cyclic, aromatic,branched, or unsaturated, and may contain linkages such as ether orester groups in the molecule. They may be primary, secondary ortertiary. Straight chain, saturated, primary amines are preferred,however, since a closer spacing of molecules can be obtained with thistype of amine, resulting in a film more impervious to corrosivematerials. Accordingly, I generally prefer to employ the straight-chainprimary octadecyl amine as the amine portion of my inhibitor.

The acid should be an organic acid since inorganic acid salts of theamines give only the inadequate protection of the amine itself. I foundthat either carboxylic or sulfonic acids are operable, although thecarboxylic acids are considerably superior to the sulfonic acids. Ineither case, the acid should contain at least 5 and preferably at least6 carbon atoms per molecule. The amine complexes of acids containingonly 5 or 6 carbon atoms give some protection but for best results theacid should contain about 10 or more carbon atoms per molecule. Acidscontaining less than 5 or 6 carbon atoms apparently fail due to highwater solubilities. As in the case of the amines, solubilityconsiderations set an upper limit of about 20 on the number of carbonatoms in the acid molecule. Again, however, this limitation can beavoided by the use of special solvents such as benzene, carbontetrachloride, ethanol or the like.

The acid may contain aromatic, cylic, ether, ester or hydroxyl groups,and may be branched or unsaturated. I prefer to use, however, straightchain, saturated, unsubstituted acids to insure close spacing of themolecules in the chemisorbed film.

The acids may be derived from several sources. In the case of thesulfonic acids, a convenient source is the petroleum sulfonic acidsproduced in acid treating of oils. Carboxylic acids may be stearic,palmitic, oleic, lauric and the like obtained from vegetable and animaloils and fats, or may be mixtures of these acids, or other mixtures ofacids such as those produced in the formation of hydrocarbons by thereduction of carbon monoxide by hydrogen over a suitable catalyst. Anyindividual member of these acid mixtures may, of course,

be isolated and used alone if desired, but some of the mix-.

tures are often preferable to avoid emulsion and gel formationdifficulties encountered when some of the purer forms of individualacids or acid mixtures are employed.

A mixture of acids is preferred because the amine complexes do not tendto form emulsions or gels, is the mixture produced from normally liquidfractions of petroleum, such as kerosene, by liquid phase partialoxidation in a process such as that described in U. S. Patent 1,690,769to Burwell. The acids should preferably be distilled, at atmosphericpressure or under a vacuum with or without steam, to remove acidslighter than valeric and heavy impurities. The acids may also bepurified by forming an aqueous solution of their salts with alkalimetals, separating the water-insoluble impurities, and then regeneratingthe organic acids by the addition of a mineral acid. I have found,however, that the impurities such as alcohols, ketones, esters, and thelike appear to exert a desirable" demulsifying and degelling action andfor that reason should be retained. Since only traces of light acids andheavy impurities are normally present in the oxidation products, the rawundistilled material, containing acids with an average molec ular weightof about to 12 or more, may be employed as the acid source withoutpurification. V v

In case serious emulsion or gel problems are encountered, demulsifiersmay be added. This is important not only to avoid the troublesomeemulsions and gels themselves, but also to improve corrosion inhibition.The explanation of less effective corrosion inhibition in the presenceof emulsions apparently is that the inhibitor is somewhatsurface-active. That is, it is concentrated at interfacial surfaces.Since this surface is great in an emulsion, most of the inhibitor willbe concentrated in these interfaces and little will remain in the bodyof the oil for deposition on the metal surfaces. In many wells,oil-in-water type emulsions often occur naturally. In such wells, theproposed amine-acid complexes, tending to form water-in-oil typeemulsions, often decrease the emulsion problems naturally present. Theamines, such as decyl amine, are convenient demulsifiers in the usualcase where an excess of amine over that required to neutralize the acidsis not objectionable.

The acid and amine may be added separately, but preferably should beadded as a salt of the acid and amine, which some authorities insist ismerely a complex and not a true salt. Two principal advantages areobtained by using a neutral salt or complex of the amine and acid.First, only one inhibitor material need be handled rather than two.Second, the oil-solubility of the complex is generally much higher thanthat of the amine or acid alone which permits handling of moreconcentrated solutions in oil. This is particularly true of the highermolecular weight materials. In addition, corrosion by either the acid oramine is eliminated if each is neutralized by the other. Since thesecorrosive effects of the unneutralized acid or amine usually are notserious, particularly in the presence of the complex, it may bedesirable in many cases to employ more of one component than the other.For example, in underground combustion work some high-molecular-weightcarboxylic acids are produced and will be present in the output wells.In this case, it may be desirable to add much more of the amine than ofthe acid, since some acid is already present in the Well. Anotherexample is when an excess of amine is employed as a demuls'ifier. In anycase, an exact neutralization of the amine and acid is not necessary,one of these components often being present in an amount as much astwice as great as the other.

When the term inhibitor is used hereinafter in both the specificationand claims, it should be understood that the term is not limited to theneutral complex of acid and amine, but may refer to an amine and an acidintroduced together or separately and in stoichiometricor otherconcentrations.

It is convenient to refer to the inhibitor as consisting of an amine andan acid, each being present in a given concentration. For example,reference may be made to adding 5 parts by weight each of the amine andthe acid per million parts of a fluid. This means the amine and acid maybe introduced simultaneously or one after the other in unreacted form orreacted to form salts with each other or with other materials. They maybe added in equal or different amounts so long as each component of theinhibitor, the amine and the acid, is present in a concentration of atleast 5 parts per million.

The amine-acid complex is usually prepared simply by mixing the acid andamine at a temperature above their melting points. The two componentsmay also be mixed with or dissolved in kerosene or other solvents beforebeing mixed together to form the reaction product. The complex issometimes prepared by forming watersoluble salts of the amine and acid,and mixing Water solutions of these salts.

In selecting the proper concentration of inhibitor to be employed, dueregard must be had for the type of fluids which are to come in contactwith the surfaces to be protected. If the fluids are principally Water,the concentration of inhibitor can be considerably lower than when thefluids are principally oil. This is probably because of the highersolubility of the inhibitor in oil than in water, resulting in a greatertendency of the oil to dissolve away the protective layer.

The quantity of inhibitor employed will also depend upon the method oftreating. In laboratory testing, it is convenient to maintain areasonably constant concentration of inhibitor continuously in fluids incontact with the test panel. The same general technique is reflected insome field practices in which an inhibitor in liquid form is allowed toflow, or is pumped at a slow continuous rate into the casing. If a solidpellet form of inhibitor is employed, a dispenser may inject a smallpellet every few minutes into the corrosive fluids where is dissolves tomaintain a fairly constant concentration of inhibitor continuously inthe fluids. Or larger pellets may be employed in which the inhibitor isdispersed in a slowlysoluble binder which gradually releases theinhibitor to maintain the latter continuously in the-corrosive fluids.Many other schemes will occur to those skilled in the art, such as theuse of a container of inhibitor from which the inhibitor escapes slowlyand continuously into the corrosive fluids through a small orifice.

A more common method of treatment and the one which I greatly prefer,since a smaller amount of inhibitor is required, is the intermittenttreatment of the well with a high concentration of inhibitor, followedby a period in which no treatment is provided. A typical treatment, forexample, consists of adding an inhibitor once a day. The entire quantityof inhibitor is introduced into a well casing inone batch and isfollowed by a quantity of oil or water to wash the inhibitor to thebottom of the Well- A common practice is to return at least a portion ofthe well production into the casing for '7 a period of to minutes, orlong enough to introduce about '20 to 50 gallons of liquids into thecasing. The result of this so-called batch treatment is to maintain fora short time an extremely high concentration of inhibitor in contactwith the metal surfaces. The concenclaims are all based .on total fluidsproduced between treatments if the intermittent-type is selected, and donot reflect the actual concentrations during the short period trationoften reaches a value of as much as 50 to 100 or more times as great aswould be present if the same quantity of inhibitor had been introducedcontinuously over a period of from 24 to 36 hours.

less inhibitor, can be employed in this method than in continuoustreatment is not'well understood, but may be because a more concentratedand imprevious filmv is de- The reason why 1 spreading the addition ofthe same amount of inhibitor out over a period of a day or so. In manywells, a large volume of oil is normally present in the annular spacebetween the tubing and casing. In these wells, even though the inhibitoris added in a batch it tends to mix with this large volume of oil and ispumped from the well over a period of a day or longer. If highconcentration inhibitor treating of such wells is desired, they mustbepumped down as far as possible before adding the inhibitor. On theother hand, continuous treatment of metal parts in a well can beobtained while employing batch addition of inhibitor to the well bybuilding up and maintaining a large volume of oil in the annulus at alltimes. I

Another indication of the advantages of a high-concentration treatmentis the benefit derived from the socalled pretreating or sluggingtechnique in which at the beginning of use of an inhibitor, theconcentration is maintained at a much higher value in the first fewtreatments than the concentration which is eventually used in normaltreatment. Use of a given amount of inhibitor in either continuous orintermittent treatment is more efiective for a considerable time aftersuch a pretreatment than without it. The explanation may be that thepretreatment provides a concentration of inhibitor on the metal surfacewhich asymptotically approaches from the high side equilibrium with thenormal treatment, whereas without the conditioning step, theconcentration on the metal surface asymptotically approaches equilibriumfrom the low side. Another possible explanation is that the highconcentration causes a continuous protective film to plate out on themetal surface. Such a film may then be easily kept in repair by thesubsequent lower-concentration treatment, whereas thelower'concentration treatment might not be capable of forming a goodprotective film in the beginning.

As a result of the above observation, the preferred method of treatmentis to pretreat the metal surface with a high concentration of inhibitorin an intermittent operation, and then employ an intermittent-type ofnormal treatment at a lower concentration.

In instances where no oil is present, as in surface injection systemsfor water-flooding operations, a concentration of only parts by weightof inhibitor per million parts of water has been found to be effectivewhen the inhibitor was introduced intermittently. The corrosiveconditions were somewhat severe in that case, so for less severeconditions, or if not quite such a high degree of protection isrequired, concentrations of the order of 5 to 10 parts per million maybe employed for intermittent treatment of relatively oil-free systems.If oil is the principal ingredient of the fluids, the normalintermittent treating concentration, based on total well fluids, shouldbe at least about 10 to 20 parts per million. The above concentrationsas well as those employed in the of the treatment unless explicitly sospecified. The period between treatmentsis generally 24 hours, but twoor more treatments may be made in one day, or they may be spread out asfar as a week apart.

If a continuous treatment is to be employed, the quantity of inhibitorshould be atleast about 10 to 20 parts per million in mildly corrosiveoil-free systems or about 20 to 50 parts per million in systemscontaining mostly oil. For oil-free systems, to 200 parts per million isconsidered a high inhibitor concentration range. For oil-containingsystems, the range may be as high as 200 to 400 parts per million inhighly corrosive areas.

In pretreating operations, concentrations as high as 50 timesthenormaltreatment which will follow are sometimes employed. The'moreusual pretreating concentrations are 10 to 20 times normal.Pretreatments normally last from 3 to 7 days or slightly more and may befol lowed by an intermediate'stageof treatment at concen' trations abouttwice normal for a period approximately equal to that of thepretreatment.

introduced in thesame manner, but in order to insure a large portion ofthe inhibitor reaching the bottom of the well in a shorttime a solutioncontaining not more than about 50 per cent of the inhibitor is usuallyemployed.

A 10 per cent solution is generally used. Although petroleum oilsolutions are most economical, solutions of the inhibitor in solventswhich are themselves soluble, in oil may also be employed. A fewexamples of such solvents I include benzene, alcohols, ethers, esters,ether alcohols available under the trademark Cellosolves and chlorinatedhydrocarbons. Use of such solvents is particuv larly desirable in thecase of high-molecular weight inhibitors of limited solubility inpetroleum hydrocarbons.

For many applications, a stick, ball, briquette, capsule, or otherpellet form of inhibitor is preferable or necessary. For example, a longcolumn of oil may be present in the annulus, preventing rapid diffusionof the inhibitor to the well pump intake. Or a packer may be set betweenthe tubing and easing requiring the inhibitor to be introduced throughthe tubing. If a pellet form is desired, it may be prepared bycompressing the powdered inhibitor, if a solid, or by use of anoil-soluble or water-soluble binder if the inhibitor is either a liquidor a solid. Some examples of oil-soluble binders are petroleum paraffin,and natural waxes such as ozokerite. Suitable water-soluble bindersinclude gelatin, the solid polyhydric alcohols, sugars, water-solublegums and ethylene oxide polymers as disclosed in copending application,S. N. 288,345, filed May 16, 1952, by Jack Barrett.

For application to systems in which the fluid is predominantly water,for example, injection systems for water-flooding projects, awater-dispersible form of inhibitor is preferred. This can be obtainedby forming pellets with a water-soluble hinder, or by emulsifying the0ilsoluble inhibitor, whether the complex, or the amines and acidsseparately, in water by use of a suitable emulsifying agent. Theemulsifying agent should be non-ionic to avoid difiiculties with theionic inhibitor and with brines. The emulsifier should be water-solubleto insure the formation of an oil-in-water emulsion. An example of suchan emulsifier is a polyoxyethylene anhydrosorbitol monooleate containingapproximately 20 oxyethylene groups This solution may be poured down permolecule. This emulsifier is available from the Atlas Powder Companyunder the trademark Tween 80.

It is to be noted that many of these emulsifiers are water-soluble orwater-dispersible waxy solids which can act as water-soluble binders forthe inhibitor. Thus, the materials may act to carry oily inhibitors, instick or other pellet form, through the oil phase and into the Waterphase where the inhibitor is dispersed into the aqueous phase by theemulsifying properties of these binder-emulsifiers. I

My invention will be further illustrated by the following specificexamples:

EXAMPLE I One series of tests was carried out as follows: Into 1 literglass bottles, 800 milliliters of an aqueous 5 per cent sodium chloridebrine were introduced together with about 16 milliliters of kerosenecontaining an amount of inhibitor equal to 400 parts by Weight permillion parts of combined brine and kerosene. Polished and tared mildsteel test panels, 1 inch by 1 inch by inch were suspended in the brineby metal rods from which the panels were insulated by plastic washers.The rods were supported, in turn, by insertion into the rubber stoppersemployed to close the bottles. A stream of corrosive gases was bubbledcontinuously through the liquids in the bottles while the temperaturewas maintained at 100 F. The corrosive gases consisted of 1 percenthydrogen sulfide and 99 per cent air. The bottles were shakenviolently for 15 consecutive minutes every two hours. At the end ofthree days, the panels were dipped in dilute inhibited hydrochloric acidsolution, rubbed lightly to remove adhering scale, rinsed in distilledwater, dried and weighed. Per cent inhibition was determined by thefollowing formula.

Where W2 is weight lost by the test panel and We is weight lost by acontrol panel exposed to the same conditions without an inhibitor.

The results of the tests are summarized in Table I.

Percent inhibition== X 100 The Armeen materials were all obtained fromArmour and Company. Armeen 18D is about 92 per cent octadecyl amine andabout 6 per cent hexadecyl amine. Armeen residue is an' impure mixtureof amines containing from 8 to 12 carbon atoms per molecule. Armeen HTis a mixture of about 70 per cent octadecyl and about 30 per centhexadecyl. Alkyl Amine JM was obtained from Rohm and Haas Company and isa branched chain octadecyl amine. As previously explained, Alox 425acids are obtained by the partial oxidation of normally liquidhydrocarbons and contains acids having an average number of carbon atomsper molecule within the range of about to 12. The material is obtainablefrom the Alox Corporation.

The relatively low inhibition when Armeen residue was used as the aminesource is probably due to the large amount of amines of low moleculerweight, leaving only a low concentration of those having at least 10carbon atoms per molecule.

The relatively high per cent inhibition using Armeen 18D alone ismisleading, since the panel was pitted. This type of corrosion wouldlead to penetration of the metal in a short time in spite of theapparently good per 10 cent inhibition. Figure 2 of the drawingillustrates this pitting.

EXAMPLE II The conditions and procedure were the same as in Example Iexcept the duration of the test was 2 days and the temperature wasmaintained at 80 F. The amine was 8(N-diethyl amine) ethyl stearate, atertiary amine in which one of the attached chains contains an esterlinkage. The acid employed for preparing the amine salt was lauric acid.The salt concentration employed was 400 p. p. in. Weight lost by thecontrol panels averaged 0.2157 gram. Weight lost by the testpanelsaveraged 0.0323 gram. Thus, inhibition was 85.0 per cent. Theentire area was protected to approximately the same degree. This exampledemonstrates the effectiveness of salts of tertiary amines, and also ofamines containing an ester linkage.

EXAMPLE III Another series of tests was conducted in the same manner asExample I except instead of bubbling air and hydrogen sulfidecontinuously through the brine, about 700 parts of hydrogen sulfide weredissolved in the brine at the start of the test, and the oxygen wasprovided by the 200 ml. of air above the oil and water in the bottles.The duration of the tests was 7 days. The results are presented in TableII. The weight lost by the control panels averaged 0.0700 gram.

Table II Percent Amine Acid Inhibi- Remarks tion octadecyl 83 UniformProtection.

Do. 90 Do.

Do 79 Do.

Do- 63 Widespread Fitting.

Do Hydrocarbon 78 Uniform Protection.

Synthesis, 7 carbon and Heavier. Sec. Octadecyl Alox 425 83 Do.

and Heptadecyl. Dodecyl 87 Do.

D 85 Do.

61 Slight Fitting and Localized etching. 71 Very Slight Shallow Fitting.95 Uniform Protection. 70 Deep Pitting and Widespread Etchmg. Oyclohexyldo 15 Deep Fitting and Localized Etching. l None --do 9 Slight Pittingand Severe Localized Attack.

Do Stearic 147 Deep Fitting and (Accel- Widespread Etcherated) ing.

Do Ricinoleic 78 Few Deep Pits and Some Localized Etching. Do Laurie 69Many deep Pits.

Dodecyl None 36 Widespread Etching and Some Pits.

Sec. Octadecyl -do 96 Few Medium Pits.

and Heptadecyl.

EXAMPLE IV The method of Example III was employed to test the inhibitingabilities of some metallicsalts' of the acids. The results are presentedin Table III.

In order to test the efiiciency of my inhibitor against hydrogen sulfidecorrosion in the absence of air, a test was set up as follows: A literof aqueous per cent sodium chloride solution was placed in a flask andprepurifled nitrogen was bubbled through it for several hours toeliminate dissolved air. Hydrogen sulfide was then introduced until itsconcentration in the brine was approximately 500 parts per million. Atthe same time, a one liter Florence flask was flushed out with oxygenfree nitrogen by inserting a tube to the bottom of the flask andallowing nitrogen to flow through the tube for several minutes. About 30ml. of kerosene, containing 200 mg. of the octadecyl amine salts of Alox425 acids were introduced into the one liter flask before this nitrogenflushing operation. The brine, containing hydrogen sulfide, was thensiphoned into the one liter flask until the liquid reached the neckthereof. A polished and tared mild steel panel was then suspended in thebrine in the flask by means of a glass hook held by the rubber stopperused to seal the flask. After swirling the flask to mix the kerosene andbrine, the kerosene was permitted to rise to the top and the flask wasallowed to sit at room temperature of about 75 F. without shaking forfive days. The panel was then removed, cleaned and weighed as describedin Example I. The loss in weight by the control panels averaged 0.0158gram. Loss in weight by the test panels was only 0.0008 gram. Thus, inspite of the low solubility of the inhibitor in the aqueous phase, theinhibition was 95 per cent complete and the protection was uniform overthe entire area.

EXAMPLE VI In order to test the ability of my inhibitor to mitigatecorrosion by low-molecular-weight organic acids and carbon dioxide,tests were made as follows: About 1 liter of an aqueous 5 per cent brinesolution was placed in a 2 liter round-bottomed flask together withabout 1 liter of kerosene. A reflux condenser was placed over the flaskand the system was freed of air by boiling the water while bubbling astream of oxygen-free carbon dioxide through the liquids for a period oftwo hours. The rate of bubbling was 1 cubic foot of carbon dioxide perhour..

To the air-free liquids 500 mg. of acetic acid were added (500 p. p. m.by weight based on the water phase). Then 200 mg. of a salt of octadecylamine and Alox 425 acids were added. A polished, tared, mild steel panelwas then suspended in the water phase in the flask on a glass rodpassing through a seal in the flask. A reflux condenser was placed onthe flask and the flask heater was adjusted to hold the temperature justat the boiling point of water. For consecutive seconds out of eachminute, the panel was raised into the oil phase. A control test was runin the same manner at the same time without inhibitor. After 24 hours,the panels were cleaned, dried and weighed as described in Example 1.Control panels lost an average of 0.1250 gram while the test panels lostan average of only 0.0084 gram. Thus, 93.3 per cent of the corrosion wasinhibited. The protection was uniform over the entire area.

EXAMPLE VII Weight lost by the control panel was 0.0115 gram.

Table IV Concentration of In- Percent Remarks hibitor. p. p. m.Inhibition 96. 5 Uniform Protection.

Do. General Corrosion; no localized pitting.

1 2 EXAMPLE VIII In a water-flooding project, water was obtained from awater well. The water contained a large amount of solids, 195,000 partsper million, and 50 parts per million of hydrogen sulfide. The casingannulus was not normally open, but some air was occasionally permittedto enter the annular space between the tubing and casing. This air foundits way to the bottom of the well and as a result some oxygen waspresent in the produced water. The well was treated by introducing intothe annulus on each of two successive days, 26 gallons of awaterdispersible form of inhibitor. On each of 12 succeeding days, 13gallons of the inhibitor were introduced in the same manner. Thewater-dispersible form of inhibitor consisted of 5 pounds per gallon ofoctadecyl amine salts of Alox 425 acids, about 10 per cent of awater-soluble, non-ionic emulsifier, about 2 per cent water, and theremainder of the gallon kerosene. The well produced about 10,000 barrels(42 gallons per barrel) per day of water having a density of about 1.1grams per milliliter. Thus, the treatment amounted to about 20 parts ofinhibitor per million parts of total brine produced. Since the inhibitorwas all added at one time in 5 gallon slugs, each slug being washed downby about 10 barrels of water, the actual concentration in the water atthe bottom of the well was about 2000 to 5000 parts per million for afew minutes. Before treatment with my inhibitor, corrosion was removingmetal at the rate of about 0.040 inch of metal thickness per year.During the treatment, metal was corroded away at the rate of about 0.007inch per year. Thus, about per cent of the corrosion was inhibited. Theprotection was uniform over the entire area.

From the above description, theories and examples, it will be apparentthat I have accomplished the objects of my invention. Specific materialsand examples are offered for the purpose of illustration only and arenot to be construed as limiting my invention; the limits of which shouldbe determined rather, by the claims.

I claim:

1. A method for inhibiting corrosion of ferrous metals by fluidscontaining water and a member of the group of corrosive materialsconsisting of hydrogen sulfide, carbon dioxide, organic acids containingfrom 2 to 4 carbon atoms per molecule, combinations of these materialswith each other, combinations of each of said corrosive materials, withoxygen and combinations of said materials with each other and oxygen,comprising adding to said fluids, per million parts of said fluids, atleast 5 parts by weight each of an aliphatic amine and of a carboxylicacid, said amine containing a hydrocarbon radical having at least 10carbon atoms per molecule, and said acid containing at least 6 carbonatoms per molecule.

2. A method for inhibiting corrosion of ferrous metals by fluidscontaining water and hydrogen sulfide comprising adding to said fluids,per million parts of said fluids, at least 5 parts by weight each of analiphatic amine and of a carboxylic acid, said amine containing ahydrocarbon radical having at least 10 carbon atoms per molecule, andsaid acid containing at least 6 carbon atoms per molecule,

3. A method for inhibiting corrosion of ferrous metals by fluidscontaining water and an organic acid containing from 2 to 4 carbon atomsper molecule comprising adding to said fluids at least 5 parts by weighteach of an aliphatic amine and a carboxylic acid per million parts ofsaid fluids, said amine containing a hydrocarbon radical having at least10 carbon atoms per molecule, and said acid containing at least 6 carbonatoms per molecule.

4. A method for inhibiting corrosion of ferrous metals by fluidscontaining water and a combination of hydrogen sulfide and oxygencomprising adding to said fluids at least 5 parts by weight each of analiphatic amine and a carboxylic acid per million parts of said fluids,said amine containing a hydrocarbon radical having at least 10 carbonatoms per molecule, and said acid containing at least 6 carbon atoms permolecule.

5. A method for inhibiting corrosion of ferrous metals by fluidscontaining water and a member of the group of corrosive materialsconsisting of hydrogen sulfide, carbon dioxide, organic acids containingfrom 2 to 4 carbon atoms per molecule, combinations of these materialswith each other, combinations of each With oxygen, and combinations witheach other and oxygen, comprising adding to said fluids at least 5 partsby weight each of an aliphatic amine and a carboxylic acid per millionparts of said fluids, said amine containing a hydrocarbon radical havingat least 12 carbon atoms per molecule, and said acid containing at leastcarbon atoms per molecule.

6. A method for inhibiting corrosion of ferrous metals by fluidscontaining water and a member of the group of corrosive materialsconsisting of hydrogen sulfide, carbon dioxide, organic acids containingfrom 2 to 4 carbon atoms per molecule, combinations of these materialswith each other, combinations of each with oxygen, and combinations witheach other and oxygen, comprising adding to said fluids at least 5 partsby weight each of octadecyl amine and acids produced from a normallyliquid fraction of petroleum by liquid phase partial oxidation of thelatter, per million parts of said fluids.

7. A method for inhibiting corrosion of ferrous metals by fluidscontaining water and a member of the group of corrosive materialsconsisting of hydrogen sulfide, carbon dioxide, organic acids containingfrom 2 to 4 carbon atoms per molecule, combinations of these materialswith each other, combinations of each with oxygen, and combinations witheach other and oxygen, comprising adding to said fluids at least 10parts by Weight of a salt of an aliphatic amine and a carboxylic acidper million parts of said fluid, said amine containing a hydrocarbonradical having at least 10 carbon atoms per molecule, and said acidcontaining at least 6 carbon atoms per molecule.

8. A method for inhibiting corrosion of ferrous metals by fluidscontaining water and a member of the group of corrosive materialsconsisting of hydrogen sulfide, car bon dioxide, organic acidscontaining from 2 to 4 carbon atoms per molecule, combinations of thesematerials with each other, combinations of each with oxygen, andcombinations with each other and oxygen, comprising adding to saidfluids at least 5 parts by weight each of an aliphatic amine and acarboxylic acid per million parts of said fluids, said amine containinga hydrocarbon radical having at least 10 carbon atoms per molecule, andsaid acid containing at least 6 carbon atoms per molecule, said amineand said acid being added as an emulsion in water stabilized by anon-ionic, water-soluble emulsifier, whereby the oil-soluble inhibitoris dispersed in the aqueous phase of said fluids.

9. A method for inhibiting corrosion of ferrous metal parts of surfaceinjection equipment of water-flooding operations by the combined actionof hydrogen sulfide and oxygen comprising adding to the water a mixturecomprising a non-ionic, Water-soluble emulsifying agent and at least 5parts by weight each of an aliphatic amine and a carboxylic acid permillion parts of said Water, said amine containing a hydrocarbon radicalhaving at least 10 carbon atoms per molecule, and said acid containingat least 6 carbon atoms per molecule, whereby the oil-solublecorrosion-inhibiting amine and acid are dispersed in the water.

10. A method for inhibiting corrosion of ferrous metals by fluidscontaining water and a member of the group of corrosive materialsconsisting of hydrogen sulfide, carbon dioxide, organic acids containingfrom 2 to 4 carbon atoms per molecule, combinations of these materialsWith each other, combinations of each of said corrosive material withoxygen and combinations of said materials with each other and oxygen,comprising adding to said fluids, per million parts of said fluids, atleast 5 parts by Weight each of an aliphatic amine and of a carboxylicacid, said amine containing a hydrocarbon radical having at least 10carbon atoms per molecule, and said acid being derived from a normallyliquid fraction of petroleum by liquid phase partial oxidation of thelatter.

11. A well-treating and corrosion-inhibiting composition comprising thesalt of an aliphatic primary amine containing a hydrocarbon radicalhaving at least about 10 carbon atoms per molecule and a mixture ofacids derived from a normally liquid fraction of petroleum by liquidphase partial oxidation of the latter.

12. A method for inhibiting corrosion of ferrous metals by fluidscontaining water and a member of the group of corrosive materialsconsisting of hydrogen sulfide, carbon dioxide, organic acids containingfrom 2 to 4 carbon atoms per molecule, oxygen, and combinations of theindividual materials, comprising adding to said fluids at least about 5parts by weight each of an aliphatic primary amine and a carboxylic acidper million parts of said fluids, said amine containing a hydrocarbonradical having at least about 10 carbon atoms per molecule, and saidacid being derived from a normally liquid fraction of petroleum byliquid phase partial oxidation of the latter.

References Cited in the file of this patent UNITED STATES PATENTS2,460,259 Kahler Jan. 25, 1949 2,468,163 Blair et al Apr. 26, 19492,583,399 Wachter et al. Jan. 22, 1952 2,599,385 Gross et al. June 3,1952 2,614,980 Lytle Oct. 21, 1952 2,614,981 Lytle Oct. 21, 19522,629,649 Wachter et al. Feb. 24, 1953 2,640,809 Nelson June 2, 19532,643,227 Hughes et al June 23, 1953 2,646,399 Hughes July 21, 19532,649,415 Sundberg et a1 Aug. 18, 1953 2,675,355 Lytle Apr. 13, 1954

1. A METHOD FOR INHIBITING CORROSION OF FERROUS METALS BY FLUIDSCONTAINING WATER AND A MEMBER OF THE GROUP OF CORROSIVE MATERIALSCONSISTING OF HYDROGEN SULFIDE, CARBON DIOXIDE, ORGANIC ACIDS CONTAININGFROM 2 TO 4 CARBON ATOMS PER MOLECULE, COMBINATIONS OF THESE MATERIALSWITH EACH OTHER, COMBINATIONS OF EACH OF SAID CORROSIVE MATERIALS, WITHOXYGEN AND COMBINATIONS OF SAID MATERIALS WITH EACH OTHER AND OXYGEN,COMPRISING ADDING TO SAID FLUIDS, PER MILLION PARTS OF SAID FLUIDS, ATLEAST 5 PARTS BY WEIGHT EACH OF AN ALIPHATIC AMINE AND OF A CARBOXYLICACID, SAID AMINE CONTAINING A HYDROCARBON RADICAL HAVING AT LEAST 10CARBON ATOMS PER MOLECULE, AND SAID ACID CONTAINING AT LEAST 6 CARBONATOMS PER MOLECULE.